Triethanolamine straight chain secondary alkylbenzene sulfonate liquid detergent compositions

ABSTRACT

A NON-GELLING AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF AN AMOUNT IN EXCESS OF ABOUT 40 WEIGHT PERCENT AND RANGING UP TO ABOUT 70 WEIGHT PERCENT OF TRIETHANOLAMINE STRAIGHT CHAIN SECONDARY ALKYLBENZENE SULFONATES AND A DEGELLING AGENT IN AMOUNTS RANGING FROM MINIMUM AMOUNTS SUFFICIENT TO PREVENT THE GELLING OF SAID SULFONATES TO MAXIMUM AMOUNTS SUFFICIENT TO PRODUCE CLEAR, FREE-FLOWING SOLUTIONS OF SAID SULFONATES.

United States Patent US. Cl. 252-437 Claims ABSTRACT OF THE DISCLOSURE A non-gelling aqueous solution consisting essentially of an amount in excess of about 40 weight percent and ranging up to about 70 weight percent of triethanolamine straight chain secondary alkylbenzene sulfonates and a degelling agent in amounts ranging from minimum amounts sufficient to prevent the gelling of said sulfonates to maximum amounts sulficient to produce clear, free-flowing solutions of said sulfonates.

This invention relates to anionic detergent compositions which contain triethanolamine salts of alkylbenzene sulfonic acids. More particularly this invention relates to nongelling, aqueous solutions containing triethanolamine salts of straight chain secondary alkylbenzene sulfonic acids.

Aqueous detergent solutions containing triethanolamine salts of alkylbenzene sulfonic acids are widely used in the home and industry in applications where it is required that the detergent formulation have the properties of high water solubility and mildness, such as in shampoo formulations. The triethanolamine salts of alkylbenzene sulfonic acids are more water soluble and less irritating than the corresponding alkali or alkaline-earth metal salts, such as the sodium and magnesium salts. Whereas the concentration of the triethanolamine alkylbenzene sulfonates normally ranges from 10 weight percent to about weight percent in the end-use product, it is expedient for the manufacturer of the detergent sulfonates to prepare concentrated aqueous solutions containing from about 45 weight percent to about 70 weight percent of the triethanolamine alkylbenzene sulfonates during the manufacturing process thereof. This concentrated solution is diluted to the extent desired at the time convenient for the preparation of the end-use product. The advantage of working with a concentrated solution is an economic one, in that the greater the amount of detergent per volume of water that can be stored or transported, the cheaper the attendant costs will be. The cost savings are substantial in view of the fact that in the detergent industry the manufacturere of the detergent sulfonate is not generally the manufacturer of the end-use product and the detergent sulfonate, consequently, must be conveyed, sometimes over long distances, from the one manufacturer to the other,

The manufacturer of the end-use product who, in addition to preparing the detergent formulation which the consumer buys, prepares concentrated specialty formulations for commercial establishments, also realizes an advantage in being able to purchase concentrated sulfonate solutions. For example, it is not uncommon for the manufacturer of the end-use product to sell concentrated shampoo formulations which contain additional ingredients along with the sulfonate to beauty salons. The large amounts of shampoo which the beauty salon operators use dictate that they buy concentrated shampoo formulations for the same reasons the manufacturer of the sulfonate prepares concentrated sulfonate solutions. If the manufacturers of the end-use product received a dilute sulfonate solution from the manufacturer of the sulfonate they would incur an additional expense by having to further concentrate the solution. However, by receiving concentrated sulfonate solutions they may add additional ingredients, that may also be dissolved in water, to the sulfonate solution with out having to resort to evaporation of the water to attain the desired high solids content in the final shampoo formulation.

Presently the bulk of the triethanolamine alkylbenzene sulfonates that are marketed commercially are mixtures of compounds that are derived from propylene polymer wherein the alkyl side chain is highly branched and contains approximately 10 to 15 carbon atoms with an average of about 12 carbon atoms. Aqueous solutions containing 1 to 62 weight percent or more of these compounds are clear, free-flowing liquids which can be stored and transported very conveniently. However, as this class of detergents is not biodegradable and since the detergent industry is striving to market only biodegradable detergents as a means of eliminating detergent pollution, these compounds are no longer desirable ingredients in detergent formulations. As it is known that straight chain secondary alkylbenzene sulfonates are biodegradable, it would seem to be a simple expedient to substitute these compounds for the corresponding branched chain compounds for use in the applications desscribed above. However, when this substitution is made, it has been found that as the concentration of triethanolamine straight chain secondary alkylbenzene sulfonates in water is increased beyond about 40 weight percent, viscous gel-like slurries are obtained and when the concentration of the straight chain sulfonates is increased to 45 and higher weight percent, non-fiowing, solid gels are formed. These gel-like slurries and non-flowing, solid gels are virtually impossible to pour and pump and generally create handling problems. Although aqueous solutions containing lower concentrations of triethanolamine straight chain secondary alkylbenzene sulfonates are non-gelling and free-flowing, their high water content makes them uneconomical to store, transport, and formulate for certain applications. It, therefore, would be extremely desirable to provide non-gelling, aqueous solutions containing in excess of about 45 weight percent triethanolarnine straight chain secondary alkylbenzene sulfonates.

It is therefore an object of this invention to provide non-gelling, aqueous solutions which contain triethanolamine straight chain secondary alkylbenzene sulfonates in an amount exceeding about 45 weight percent. It is a further object of this invention to provide a method for producing non-gelling, aqueous solutions which contain triethanolamine straight chain secondary alkylbenzene sulfonates in an amount exceeding about 45 weight percent.

Other objects will become apparent from the description of the invention and from the claims.

In accordance with the instaant invention it has been found that about 45 to about weight percent aqueous solutions of triethanolamine straight chain secondary alkylbenzene sulfonates to which has been added certain inorganic and metallo-organic salts, are non-gelling compositions. It has also been found that these salts, hereinafter referred to as degelling agents, are effective in increasing the solubility and decreasing the viscosity of the gel-like slurries. Therefore, it should be understood that the term solution as used herein and in the claims includes homogeneous clear solutions and also non-gelling slurries wherein some solid sulfonate particles are in equilibrium with the solution. The effective degelling agents are as follows: alkali metal and ammonium salts of chloride, acetate, citrate, bisulfite, sulfite, and sulfate; alkali metal phosphates; aluminum salts of chloride and sulfate; alkaline earth chlorides; and magnesium sulfate. The degelling agent or mixtures thereof may be incorporated into aqueous solutions of triethanolamine straight chain secondary alkylbenzene sulfonates in minimum amounts, that is in amounts just sufiicient to prevent said sulfonate solution from forming a solid gel, or additional amounts of the degelling agent may be added to increase the solubility and decrease the viscosity of the slurry to the extent desired. The effective amounts of degelling agent will vary depending on the particular compound used and the concentration of the triethanolamine straight chain secondary alkylbenzene sulfonates in aqueous solution in that more concentrated solutions will require higher amounts of the degelling agent. The amount of degelling agent required will also depend upon the degree of water solubility of the particular triethanolamine straight chain secondary alkylbenzene sulfonates being utilized. For instance, those compounds with the shorter side chain will require less degelling agent. Generally there will be required the presence of about 0.5 weight percent degelling agent, although the more highly concentrated sulfonate solutions may required as much as about 3.0 weight percent degelling agent. In instances where it is also desired to increase the solubility and decrease the viscosity of the gel-like sulfonate slurry, slightly higher amounts of degelling agent are necessary.

The triethanolamine alkylbenzene sulfonates which form gels in concentrated aqueous solutions as hereinabove described are characterized by having a straight alkyl side chain containing 9 to 15 carbon atoms wherein the alkyl side chain is attached to a carbon atom of the benzene nucleus at a secondary carbon atom of the chain. Normally detergent formulations are prepared from mixtures of the above compounds wherein the average number of carbon atoms in the alkyl side chain range from 10 to 13. The carbon number spread of the alkyl side chain may range as high as 7, as in mixtures which contain 9 to carbon atoms in the alkyl side chain, or as low as 2. The preferred mixture is triethanolamine straight chain secondary alkylbenzene sulfonates that has a carbon number spread of three or four wherein the average number of carbon atoms in the alkyl side chain is 11 to 12. These blends of compounds have excellent overall surface active properties.

The triethanolamine straight chain secondary alkylbenzene sulfonates used in this invention may be prepared by any one of a number of well-known methods. For example, a halogenated normal paraffin which contains from 9 to 15 carbon atoms and which is obtained by monochlorinating the corresponding paraflin can be treated with an excess of benzene in the presence of a suitable alkylation catalyst of the Friedel-Crafts type, such as aluminum chloride, to obtain substantial yields of secondary straight chain alkylated benzene. These alkylated benzene compounds may also be prepared by alkylating benzene with a normal alcohol or a normal mono-olefin containing 9 to 15 carbon atoms in the presence of a Friedel-Crafts catalyst. The alkylated benzenes having a straight chain alkyl group containing from 9 to 15 carbon atoms or a mixture of alkylated benzenes within this carbon number range is then subjected to sulfonation. This may be accomplished with oleum, sulfuric acid or sulfur trioxide. If sulfur trioxide is used, the sulfonic acids may be directly neutralized with triethanolamine in the presence of a suitable amount of water to obtain the desired solids concentration for the final product. If sulfuric acid or oleum is used for sulfonation, spent acid must first be settled out. This may be rendered faster and more complete by dilution of the reaction mixture with a solvent such as benzene or hexane or mixtures thereof. The sulfonic acids may then be extracted from the benzene or hexane solvent with water and methanol or other low molecular weight alcohol solution, to purify the sulfonic acids of any unreacted hydrocarbon or any hydrocarbon soluble by-products such as sulfones. The sulfonic acids in the aqueous alcohol solution are then neutralized with triethanolamine. The alcohol is removed from the neutralized sulfonate solution by stripping and a concentrated aqueous solution of the triethanolamine sulfonate is prepared by evaporation of a suitable amount of water.

Exemplary alkali metal and ammonium slats suitable for use in the practice of this invention are lithium chloride, ammonium chloride, lithium acetate, potassium acetate, ammonium acetate, lithium citrate, potassium citrate, ammonium citrate, lithium bisulfite, potassium bisulfite, ammonium bisulfite, lithium sulfate and ammonium sulfate.

The alkali metal phosphate suitable for use in the practice of this invention are alkali metal metaphosphates, preferably alkali metal hexametaphosphate, alkali metal pyrophosphates, alkali metal and alkali metal hydrogen orthophosphates and alkali metal tripolyphosphates. Preferably the alkali metals are lithium, sodium or potassium. Exemplary compounds are lithium metaphosphate, potassium hexametaphosphate, sodium pyrophosphate, potassium pyrophosphate, lithium orthophosphate, potassium orthophosphate, lithium di-hydrogen orthophosphate, potassium di-hydrogen orthophosphate, sodium mono-hydrogen orthophosphate and potassium mono-hydrogen orthophosphate.

The alkaline earth metal salts suitable for use in the practice of this invention are magnesium chloride, calcium chloride and magnesium sulfate. Barium chloride, calcium sulfate and barium sulfate are ineffective degelling agents.

The aluminum salts which prevent the gelling of the triethanolamine straight chain secondary alkylbenzene sulfonates are aluminum chloride and aluminum sulfate.

The preferred salts for use in the compositions of this invention are sodium sulfate, ammonium sulfate, calcium chloride, magnesium chloride, aluminum sulfate, aluminum chloride and sodium acetate.

In the detergent industry it is common practice to have present relatively large amounts of inorganic salts in a solid or powdered detergent product. On the other hand, it is usually desirable to have present little or no inorganic salts in liquid formulations, because the salt decreases the solubility of the detergent formulation. For example, sodium alkylbenzene sulfonate usually contains 5 to 15 weight percent of sodium sulfate as a result of the manufacturing process. When the sulfonate is marketed as a powdered detergent product the sodium sulfate is allowed to remain with the sulfonate and it is even conventional to add additional amounts of sodium sulfate because it is a cheap, inert filler. However, for aqueous sulfonate products, whether formulated as a final consumer product or not, it is desirable to have the lowest possible sodium sulfate content in order to have good solubility. For this reason, sodium sulfate is never purposely added to sodium alkylbenzene sulfonate which is to be used in a liquid formulation. Other inorganic salts are for the same reason kept out of most liquid detergent formulations, with a few special exceptions. For example, alkali metal phosphates and silicates are commonly used in liquid laundry detergents and liquid all-purpose cleaners because of their beneficial cleansing or corrosion inhibition properties although these salts decrease the solubility of the formulation.

However triethanolamine alkylbenzene sulfonates are used almost entirely in special applications where extreme mildness and excellent solubility are of the utmost importance. In these applications alkaline inorganic salts such as phosphates, silicates, and carbonates, and neutral salts, such as sodium sulfate and sodium chloride have not been used because it has been generally thought that they would serve no useful purpose and would adversely affect the water solubility of the liquid formulation. In view of the lower solubility usually obtained when a product contains inorganic salts, it was quite surprising and unexpected to discover that the degelling agents of this invention not only prevented the triethanolamine straight chain secondary alkylbenzene sulfonates from gelling but also improved the solubility and viscosity of the aqueous sulfonate solution. It has also been found that the degelling agents utilized in the compositions of this invention do not have any deleterious effect on the over-all performance of the product.

The compositions of this invention may be prepared in various Ways, the choice of which depends on the method used to sulfonate the alkylated benzene. When the alkylated benzene is sulfonated with sulfuric acid or oleum, and a hydrocarbon solvent and an alcohol-water extraction is used to aid in separating spent acid, and in purifying the sulfonic acids, the triethanolamine sulfo nate solution resulting from neutralization is usually less than 40 weight percent solids. The degelling agent can be added at any time before or during concentration by distillation or evaporation to the desired high solids content of about 45 to 70 weight percent. For practical ease in mixing and concentrating, the degelling agent is preferably added at any time before the gel-like slurry forms.

When the alkylated benzene is sulfonated with sulfur trioxide or with sulfuric acid or oleum without the use of solvents to aid in separating spent acid or unreacted hydrocarbons, common practice is to neutralize the alkylbenzene sulfonic acids with triethanolamine in the presence of the necessary amount of water to give directly the desired solids content of the final product. In this case, an aqueous solution containing triethanolamine and degelling agent should be prepared. The alkylbenzene sulfonic acids are then admixed with this aqueous solution for reaction to form the non-gelling triethanolamine alkylbenzene sulfonate.

Another method may be utilized to prepare the compositions of this invention when the degelling agent is a salt which contains the sulfate anion, e.g. sodium sulfate, ammonium sulfate, magnesium sulfate, etc. (This method may be utilized regardless of the manner in which the alkylated benzene is sulfonated.) It has been found that the sulfate salt can :be formed in situ after the alkylated benzene has been sulfonated. This is accomplished by adding the desired stoichiometric quantity of a hydroxide or oxide salt of the selected cation to the sulfonic acid mixture. For example, sodium hydroxide, ammonium hydroxide or magnesium oxide may be added to the sulfonic acid mixture prior to or during the neutralization of the alkylbenzene sulfonic acids with the triethanolamine. The base is preferably added prior to the neutralization step.

The examples included in Table I below serve to illustrate and compare the gelling properties of aqueous solutions of triethanolamine salts of branched chain and straight chain alkylbenzene sulfonic acids. The triethanolamine branched chain alkylbenzene sulfonates are a mixture of compounds containing from 9 to 15 carbon atoms in the a-lkyl side chain with an average of about 12 carbon atoms and are derived from the sulfonation by sulfuric acid of alkylate produced from propylene tetramer and benzene using AlCl catalyst. The triethanolamine straight chain secondary alkylbenzene sulfonates are a mixture of compounds containing 9 to 14 carbon atoms in the side chain with an average of about 12 carbon atoms and are derived from the sulfonation by sulfuric acid of alkylate produced from alpha olefins and benzene using A101 cata'lyst. The numbers which appear under the column headed Amount of Detergent in Weight Percent refer to the total weight percent solids present in the aqueous composition. The solids, in addition to the alkylbenzene sulfonates, contain the normal amounts of by-products such as triethanolamine sulfate and triethanolamine, which are present in a commercially manufactured product. The alkylbenzene sulfonates comprise about 90 weight percent of the total solids present.

TABLE I Aqueous composition liquid.

The table illustrates the unexpected difference in the gelling properties of triethanoamine branched and straight chain alkylbenezene sulfonates. Moreover, it was surprising to find that the monoand diethanolamine salts of straight chain secondary alkylbenzene sulfonates do not form a solid gel in concentrated aqueous solutions. They form fiowable slurries and as such behave similarly to their corresponding branched chain sulfonates.

It was also surprising to find that the triethanolamine straight chain secondary alkylbenzene sulfonates are only about 40 weight percent water soluble. The fact that the triethanolamine branched chain alkylbenzene sulfonates are about three times more water soluble than the corresponding sodium sulfonates (about 60 weight percent vs. 20 weight percent) coupled with the fact that the sodium salts of straight chain secondary alkylbenzene sulfonic acids are almost twice as soluble as the sodium salts of branched chain alkylbenzene sulfonic acid (about 35 weight percent vs. 20 weight percent) would lead one to expect that the triethanolamine straight chain secondary alkylbenzene sulfonates would be much more water soluble than the corresponding sodium sulfonates and consequently have a water solubility much in excess of 40 weight percent. However, it should be understood that it is not primarily lack of water solubility that creates the practical problems associated with triethanolamine straight chain secondary alkylbenzene sulfonates because the corresponding sodium sulfonates which are slightly less soluble can be concentrated up to 60 weight percent in Water and still remain a flowa ble gel-like slurry at room temperature that can be pumped and handled albeit some difliculty. It is the fact that the triethanolamine straight chain secondary alkylbenzene sulfonates at concentrations in excess of about 45 weight percent in water are a solid gel that prevents their use in commerce.

The examples included in Table II below serve to describe specific compositions of this invention, the effectiveness of the degelling agents hereinabove described, and the approximate range of amounts of degelling agents required to produce non-gelling compositions. It will be noted that some of the compositions listed in the table are gel-like, although they contain compounds described herein as effective degelling agents. These compositions are included to indicate the criticality of using a sufficient amount of degelling agent. It should be understood that non-gelling compositions are obtained by adding additional amounts of the degelling agent to the composition. The triethanolamine straight chain secondary alkylbenzene sulfonate is the same as that used in the examples presented in Table I, with the exception that some of the sulfonates were derived from chloroparaffins instead of alpha olefins. The source of the alkylating agent is not critical The compositions were prepared simply by admixing the degelling additives with aqueous solutions of the sulfonate compounds and evaporating a sufficient amount of water to obtain the stated concentrated products.

TABLE II Aqueous composition TEA straight Degelling chain secondary Descripadditive alkylbenzene tion of Ex. in wt. sulfonate in compo- No. Degelhng additive percent weight percent sition 1 8 Sodium chloride 3. 57 l S) Potassium chloride 1.0 50 3 10 Sodium acetate. 2.0 60 1 11 Sodium citrate-.. 3.0 57 1 12 Sodium bisulfitc. 2. (l 60 2 13..." Sodium suliite... 1.0 50 2 14 Sodium sulfate 3. 0 57 1 15 do 2. 0 58 l d0 1.0 59 4 17... Potassium sulfa 1.0 50 2 l8... Sodium hexametaphosphate- 1. 0 5O 2 19 Sodium pyrophosphato 1.0 50 3 20"... Potassium pyrophosphatd. 1. 0 5L) 3 21 Sodium orthophosphate 1.0 3 Sodium di-hydrogen orthophosphate. 2. O 2 Sodium tripolyphosphatc 3.0 57 1 Ammonium chloride 1. 0 5.) 4 1.0 50 2 2. 0 50 l 1. 0 50 l 2. 0 6O 3 l 2. 0 60 l 30 Aluminum sulfate 1. 0 50 2 X 1Clear, free-flowing liquid; 2HaZy liquid; 3Hazy gel, slight flow when inverted;

4- Gel, no flow when inverted.

2 CaClz is very effective as a degelling additive. However Ca reacts with any S04 present from the sulfonation of the alkylbenzene to form insoluble CaSOt. The precipitate may be settled or filtered from the solution.

Oddly enough some salts although similar to those used effectively as degelling agents are ineffective as degelling agents. The compositions included in Table III below serve to illustrate some of the inorganic salts and organic salts that were found to be ineffective degelling agents. The triethanolamine straight chain secondary alkylbenzene sulfonate is the same as that used in the compositions of Tables I and II.

TABLE III philic end oriented away from the center. It is theorized that the hydrogen in the OH group of the triethanolamine salt hydrogen bonds to adjacent molecules in the same micelle giving a rigid structure to the micelle and, consequently a gel is formed. It is also theorized that the effective salts described herein inhibit gelling by preventing hydrogen bonding due to the greater electrolyte concentration in the solution. It is also thought that concentrated Aqueous composition TEA straight A significant feature of the degelling agents of this inversely affect the good over-all properties desired of a liquid detergent formulation. If higher amounts of salts had to be added to the liquid detergent formulation to prevent the gelling of the sulfonates, a host of additional problems would occur. For instance, the presence of higher amounts of salts could adversely affect the viscosity, pH and mildness properties of the liquid formulation. Also the compatibility or solubility of additional components that might be added could be lessened. (The particular property or properties adversely affected would, of course, depend on the type of salt used.) Therefore, it is conceivable that the ineffective salts included in Table III or perhaps other salts would, if used in higher concentrations, produce non-gelling compositions, but they would be undesirable from a practical standpoint due to additional problems that would arise because of the higher salt content in the liquid formulation.

The phenomenon of gel formation of concentrated aqueous compositions of triethanolamine straight chain secondary alkylbenzene sulfonate and the behavior of the degelling agents is not completely understood. However it is generally accepted that the triethanolamine straight chain secondary alkylbenzene sulfonate molecules form micelles with the hydrophobic end of each molecule oriented toward the center of the micelle and the hydroaqueous compositions of triethanolamine branched chain alkylbenzene sulfonates do not gel because the branching in the alkyl side chain keeps the individual molecules in the micelle a distance far enough apart to prevent hydrogen bonding and hence gel structures.

It is understood that the above explanation should in no way be construed to limit the claimed compositions of this invention.

The compositions of this invention are useful as bubble bath detergents or fine fabric detergents. When so used, small amounts of additional ingredients, such as perfumes and dyes, may be added to the compositions for aesthetic purposes. On the other hand, the compositions of this invention may be diluted with Water or formulated with additional ingredients to prepare detergents suitable for use in other applications, such as shampoos.

We claim:

1. A non-gelling aqueous solution consisting essentially of an amount in excess of about 45 weight percent and ranging up to about weight percent of triethanolamine straight chain secondary alkylbenzene sulfonates, said sulfonates having a straight alkyl side chain length of 9 to 15 carbon atoms, and in a degelling amount ranging from 0.5 to 3.0 weight percent, a degelling agent having the structural formula:

wherein C is a monovalent cation selected from the group consisting of sodium and potassium; A is an anion selected from the group consisting of acetate, chloride, citrate, sulfate and tripolyphosphate and it corresponds to the valence of A.

2. A composition according to claim 1 wherein the degelling agent is sodium acetate.

3. A composition according to claim 1 wherein the degelling agent is sodium sulfate.

4. A composition according to claim 1 wherein the degelling agent is sodium tripolyphosphate.

5. A composition according to claim 1 wherein the degelling agent is sodium citrate.

6. A non-gelling aqueous solution consisting essentially of about 60 weight percent of triethanolamine straight chain secondary alkylbenzene sulfonates, said sulfonates having straight alkyl side chain length of 9- to 15 carbon atoms, and, in a degelling amount ranging from 0.5 to 3.0 weight percent, a degelling agent having the structural formula:

wherein C is a monovalent cation selected from the group consisting of sodium and potassium; A is an anion selected from the group consisting of acetate, chloride, citrate, sulfate and tripolyphosphate and 11 corresponds to the valence ofA.

7. A composition according to claim 6 wherein the degelling agent is sodium acetate.

10 8. A composition according to claim 6 wherein the degelling agent is sodium sulfate.

9. A composition according to claim 6 wherein the degelling agent is sodium tripolyphosphate.

10. A composition according to claim 6 wherein the degelling agent is sodium citrate.

References Cited UNITED STATES PATENTS LEON D. ROSDOL, Primary Examiner M. HALPERN, Assistant Examiner US. Cl. X.R. 252152 

